How to select multiple layers on the Timeline?

In the Timeline, you can select multiple layers in two different ways.

To include multiple consecutive layers in your selection: first click the top layer, then hold down the Shift key and then click on the bottom layer to highlight all of the layers in between.

To select multiple non-consecutive layers, hold down the Ctrl key (PC) or the Cmd key (Mac) and then click on each layer you'd like to select.

Once selected, you can apply common actions to your selection, for example:

Shifting the objects in time while preserving their relative timing: while multipe layers are selected, grab the time bar of one of the objects (click and hold) and drag it left or right. The other selected objects will also shift with the first one.

Reduce the length (in time) of your objects: drag the edge of the time bar of one of the objects left or right. The edge(s) of the other selected objects will also shift accordingly:

Please also note you can drag the whole Clip by its grey bar to shift it in time (left or right).